The Internet has become a mainstream network for communicating not just data, such as email and pictures, but also for providing real-time bi-directional voice communications. Voice Over Internet Protocol (VoIP) is an industry standard that has evolved to enable users to place phone calls through the Internet, instead of through the Public Switched Telephone Network (PSTN). A conventional phone or other Consumer Premises Equipment (CPE) may now be connected to the Internet using an interface device that converts analog phone signals to digital signals that can be communicated through the Internet. A phone call may thereby be communicated through the Internet to a VoIP provider, who converts the call back to an analog signal and places the call through the PSTN that is local to the called phone. A user can thereby dial a telephone number in a conventional manner and have the call routed through the Internet, instead of through the PSTN.
The availability of the PSTN for a user may be tested by determining whether a dial tone is received from the PSTN. However, in a VoIP system the dial tone can be generated by the CPE itself or by an interface device that connects the CPE to the VoIP system. Accordingly, a VoIP system may need to be tested differently than the PSTN system.